1. Field of the Invention
The present invention relates to a multicomponent fiber. The multicomponent fiber comprises an unreacted mixture of an aliphatic polyester polymer as a continuous phase, polyolefin microfibers as a discontinuous phase encased within the aliphatic polyester polymer continuous phase, and a compatibilizer for the aliphatic polyester polymer and the polyolefin microfibers. The multicomponent fiber exhibits substantial biodegradable properties yet is easily processed. The multicomponent fiber is useful in making nonwoven structures that may be used in a disposable absorbent product intended for the absorption of fluids such as body fluids.
2. Description of the Related Art
Disposable absorbent products currently find widespread use in many applications. For example, in the infant and child care areas, diapers and training pants have generally replaced reusable cloth absorbent articles. Other typical disposable absorbent products include feminine care products such as sanitary napkins or tampons, adult incontinence products, and health care products such as surgical drapes or wound dressings. A typical disposable absorbent product generally comprises a composite structure including a topsheet, a backsheet, and an absorbent structure between the topsheet and backsheet. These products usually include some type of fastening system for fitting the product onto the wearer.
Disposable absorbent products are typically subjected to one or more liquid insults, such as of water, urine, menses, or blood, during use. As such, the outer cover backsheet materials of the disposable absorbent products are typically made of liquid-insoluble and liquid impermeable materials, such as polypropylene films, that exhibit a sufficient strength and handling capability so that the disposable absorbent product retains its integrity during use by a wearer and does not allow leakage of the liquid insulting the product.
Although current disposable baby diapers and other disposable absorbent products have been generally accepted by the public, these products still have need of improvement in specific areas. For example, many disposable absorbent products can be difficult to dispose of. For example, attempts to flush many disposable absorbent products down a toilet into a sewage system typically lead to blockage of the toilet or pipes connecting the toilet to the sewage system. In particular, the outer cover materials typically used in the disposable absorbent products generally do not disintegrate or disperse when flushed down a toilet so that the disposable absorbent product cannot be disposed of in this way. If the outer cover materials are made very thin in order to reduce the overall bulk of the disposable absorbent product so as to reduce the likelihood of blockage of a toilet or a sewage pipe, then the outer cover material typically will not exhibit sufficient strength to prevent tearing or ripping as the outer cover material is subjected to the stresses of normal use by a wearer.
Furthermore, solid waste disposal is becoming an ever increasing concern throughout the world. As landfills continue to fill up, there has been an increased demand for material source reduction in disposable products, the incorporation of more recyclable and/or degradable components in disposable products, and the design of products that can be disposed of by means other than by incorporation into solid waste disposal facilities such as landfills.
As such, there is a need for new materials that may be used in disposable absorbent products that generally retain their integrity and strength during use, but after such use, the materials may be more efficiently disposed of. For example, the disposable absorbent product may be easily and efficiently disposed of by composting. Alternatively, the disposable absorbent product may be easily and efficiently disposed of to a liquid sewage system wherein the disposable absorbent product is capable of being degraded.
Although degradable monocomponent fibers are known, problems have been encountered with their use. In particular, known degradable fibers typically do not have good thermal dimensional stability such that the fibers usually undergo severe heat-shrinkage due to the polymer chain relaxation during downstream heat treatment processes such as thermal bonding or lamination.
In contrast, polyolefin materials, such as polypropylene, typically exhibit good thermal dimensional stability but also have problems associated with their use. In particular, polyolefin fibers typically are hydrophobic and, and such, exhibit poor wettability, thus limiting their use in disposable absorbent products intended for the absorption of fluids such as body fluids. Although surfactants can be used to improve the wettability of polyolefin fibers, the use of such surfactants introduces additional problems such as added cost, fugitivity or permanence, and toxicity. Furthermore, polyolefin fibers are generally not biodegradable or compostable.
It would therefore be desirable to prepare a fiber that exhibits the thermal dimensional stability of polyolefin materials yet is substantially biodegradable and is wettable without the use of surfactants. A simple solution to this desire would be to simply mix a polyolefin material with a degradable material so as to gain the benefits of using both materials. However, the components of a multicomponent fiber generally need to be chemically compatible, so that the components effectively adhere to each other, and have similar rheological characteristics, so that the multicomponent fiber exhibits minimum strength and other mechanical and processing properties. It has therefore proven to be a challenge to those skilled in the art to combine components that meet these basic processing needs as well as meeting the desire that the entire multicomponent fiber be effectively substantially degradable and hydrophilic.
It is therefore an object of the present invention to provide a multicomponent fiber which is substantially degradable in the environment.
It is also an object of the present invention to provide a substantially degradable multicomponent fiber which has good thermal dimensional stability and is hydrophilic without the substantial use of surfactants.
It is also an object of the present invention to provide a substantially degradable multicomponent fiber which is easily and efficiently prepared and which is suitable for use in preparing nonwoven structures.